1. Field of the Invention
The present invention relates to a process control system.
Priority is claimed on Japanese Patent Application No. 2012-068042, filed Mar. 23, 2012, the content of which is incorporated herein by reference.
2. Description of the Related Art
All patents, patent applications, patent publications, scientific articles, and the like, which will hereinafter be cited or identified in the present application, will hereby be incorporated by reference in their entirety in order to describe more fully the state of the art to which the present invention pertains.
Conventionally, in plants and factories (hereinafter collectively referred to simply as plants), process control systems are implemented, which control various state quantities such as pressure, temperature, and flow amount in industrial processes, and a high level of automated operation is achieved. In these process control systems, in order to achieve a high level of control while securing safety, control systems such as distributed control systems (DCSs) and safety systems, such as safety instrumented systems (SISs), are provided.
In the above-noted distributed control systems, on-site devices called field devices such as measuring instruments and actuators and controllers that control the field devices are connected via a communication means, the controllers collect measurement data measured by the field devices, controlling various state quantities by actuating (controlling) field devices in accordance with the collected measurement data. The above-noted safety instrumented systems, by stopping the plant reliably in a safe condition when an emergency occurs, prevent accidents involving bodily injury and environmental pollution, and protect high-cost equipment.
The above-noted distributed control systems are generally subjected to various tests before the plant is built and operated. For example, a connection test to verify whether various field devices and controllers are properly connected and an operational verification tests to verify whether control programs used in the controllers are operating normally. In this case, the above-noted connection test cannot be performed unless the field devices and the controllers are installed in the plant and actually connected. In contrast, Japanese Unexamined Patent Application, First Publication No. 2004-29910 and Japanese Unexamined Patent Application, First Publication No. 2008-21135 disclose art enabling the above-noted operational verification test even in the condition in which there are no field devices (and no communication means connecting the field devices and the controllers).
In most conventional process control system, field devices and controllers are connected via an analog transmission line (for example, a transmission line used in 4 to 20 mA signal transmission), with analog signals being transmitted and received via analog transmission lines. In contrast, in order to implement a high level of functionality, in many process control systems in recent years, controllers and field devices are connected via a cable or wireless network, and digital signals are transmitted and received via a cable or wireless network.
In a conventional process control system, because there are direct one-to-one connections between field devices and interfaces of the controllers, once the tasks of installing and connecting the field devices and the controllers is completed, analog signal transmission and reception have been possible between the field devices and the controllers without a major problem. In process control system in recent years, however, in order to provide field devices with advanced functionality by digitization, the amount of data of the digital signals transmitted and received increases, and in order to achieve normal, safe operation, it is important to verify, for example, the following items (1) to (3) throughout the entire process control system.
(1) The influence on overall system performance by an increase in the amount of data.
(2) Whether or not the operating state of the highly functional field device is optimal (whether or not the device parameters of intelligent field devices are optimally set).
(3) The communication quality via the network and the system controllability under the influence thereof.
The above-noted item (1) is, for example, verified by measuring the degree of load on the network and the degree of load on the CPU (central processing unit) provided in the controllers. The above-noted item (2) is verified not only by judging with regard to the contents of the device parameters set in the individual field devices, but also by whether or not alarms and events notified from the field devices are proper. The above-noted item (3) is verified by measuring jitter, amount of delay, and number of re-transmissions, for example, when communicating via a network.
Such items, which apply throughout the entire process control system, basically cannot be verified unless the process control system is actually operating in a plant that is operating. For this reason, the tasks of verifying the above-noted items can be thought of as being performed after the commissioning task (task of performing trial runs of the plant to verify performance). However, if an abnormality is discovered in the verification tasks performed after the commissioning task, it is necessary to return to and correct the condition before the commissioning task was performed and then performing the commissioning task once again, this leading to the problem of extremely low efficiency. Also, when the commissioning task is performed, it is necessary to actually run material (samples) through the plant, thereby leading to a problem of cost as well.